A system capable of depositing a matrix film containing a low amount of impurities (e.g. neutral particles) is provided. The system includes: a first plate electrode 120 having an attachment surface on which a sample plate P is to be attached; a second plate electrode 130 arranged so as to face the attachment surface; a nozzle 110 for spraying a liquid containing a matrix substance into the space between the two electrodes 120 and 130 by an electrospray method, the nozzle 110 arranged so that none of the electrodes 120 and 130 lies on the central axis A of a spray flow of the liquid; and an electric field creator 140 for creating, between the two electrodes 120 and 130, an electric field for forcing electrically charged droplets contained in the spray flow of the liquid containing the matrix substance to move toward the attachment surface.